Solid-state image pickup apparatus, and image pickup system using solid-state image pickup apparatus

ABSTRACT

A solid-state image pickup apparatus includes a photoelectric conversion unit, a charge storage unit, and a floating diffusion unit, all disposed on a semiconductor substrate. The solid-state image pickup apparatus further includes a first gate electrode disposed on the semiconductor substrate and extending between the photoelectric conversion unit and charge storage unit, and a second gate electrode disposed on the semiconductor substrate and extending between the charge storage unit and the floating diffusion unit. The solid-state image pickup apparatus further includes a light shielding member including a first part and a second part, wherein the first part is disposed over the charge storage unit and at least over the first gate electrode or the second gate electrode, and the second part is disposed between the first gate electrode and the second gate electrode such that the second part extends from the first part toward a surface of the semiconductor substrate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

One disclosed aspect of the embodiments relates to a solid-state imagepickup apparatus and an image pickup system using a solid-state imagepickup apparatus, and more particularly, to a light shielding member ofa solid-state image pickup apparatus having a charge storage unitdisposed in each pixel.

2. Description of the Related Art

In an active pixel-type solid-state image pickup apparatus typified by aCMOS image sensor, it has been proposed to provide a global electronicshutter function.

The global electronic shutter function refers to a function ofperforming accumulation of a photo charge in a plurality of pixelsarranged in a matrix such that the accumulation of the photo charge isstarted and ended simultaneously for all pixels. In the solid-stateimage pickup apparatus having the global electronic shutter function,each pixel includes a photoelectric conversion unit and a charge storageunit configured to store the charge generated via the photoelectricconversation for a particular period. In the charge storage unit of thesolid-state image pickup apparatus having the global electronic shutterfunction, the charge is stored over a period from the end of theaccumulation of the photo charge to the start of reading the charge.During this period, if an electric charge generated elsewhere other thanthe photoelectric conversion unit intrudes into the charge storage unit,noise occurs which may result in degradation in image quality. JapanesePatent Laid-Open No. 2008-004692 discloses a structure in which eachpixel includes a photoelectric conversion unit and a charge storageunit, and a light shielding member is disposed over the charge storageunit.

In the structure disclosed in Japanese Patent Laid-Open No. 2008-004692,the light shielding member is disposed on an interlayer insulating filmincluding a wiring layer. In this structure, oblique light may easilyintrude into the charge storage unit via an opening of the lightshielding member. In a case where a contact is disposed for use insupplying a voltage to an element, it is necessary that an opening for aplug of the contact is formed in the light shielding member. This makesit easier for oblique light to intrude into the charge storage unit. Ifthe electric charge produced by such oblique light is mixed with animage charge stored in the charge storage unit, degradation in imagequality occurs.

In view of the above, embodiments provide a solid-state image pickupapparatus having a charge storage unit with an improved light shieldingperformance, and an image pickup system using such a solid-state imagepickup apparatus.

SUMMARY OF THE INVENTION

According to an aspect of the embodiments, a solid-state image pickupapparatus includes a semiconductor substrate, a photoelectric conversionunit disposed on the semiconductor substrate, a charge storage unit thatis disposed on the semiconductor substrate and that stores an electriccharge generated in the photoelectric conversion unit, a floatingdiffusion unit which is disposed on the semiconductor substrate and towhich the electric charge stored in the charge storage unit istransferred, a first gate electrode disposed on the semiconductorsubstrate such that the first gate electrode extends between thephotoelectric conversion unit and the charge storage unit and such thatthe first gate electrode reaches the charge storage unit, a second gateelectrode disposed on the semiconductor substrate such that the secondgate electrode extends between the charge storage unit and the floatingdiffusion unit, and a light shielding member including a first part anda second part wherein the first part is disposed over the charge storageunit and at least over the first gate electrode and the second gateelectrode, and wherein the second part is disposed between the firstgate electrode and the second gate electrode such that the second partextends from the first part toward a surface of the semiconductorsubstrate.

Further features of the disclosure will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram of a solid-state image pickup apparatusaccording to a first embodiment.

FIG. 2A is a schematic plan view of the solid-state image pickupapparatus according to the first embodiment.

FIG. 2B is a schematic cross-sectional view of the solid-state imagepickup apparatus according to the first embodiment.

FIG. 3A is a schematic cross-sectional view for use in illustrating thesolid-state image pickup apparatus according to the first embodiment.

FIG. 3B is a schematic cross-sectional view for use in illustrating thesolid-state image pickup apparatus according to the first embodiment.

FIG. 4A is a schematic plan view of a solid-state image pickup apparatusaccording to a second embodiment.

FIG. 4B is a schematic cross-sectional view of the solid-state imagepickup apparatus according to the second embodiment.

FIG. 5A is a schematic plan view of a solid-state image pickup apparatusaccording to a third embodiment.

FIG. 5B is a schematic cross-sectional view of the solid-state imagepickup apparatus according to the third embodiment.

FIG. 6A is a schematic plan view of a solid-state image pickup apparatusaccording to a fourth embodiment.

FIG. 6B is a schematic cross-sectional view of the solid-state imagepickup apparatus according to the fourth embodiment.

FIG. 6C is a schematic cross-sectional view of the solid-state imagepickup apparatus according to the fourth embodiment.

DESCRIPTION OF THE EMBODIMENTS

According to an embodiment, a solid-state image pickup apparatusincludes a photoelectric conversion unit, a charge storage unit, and afloating diffusion unit, which are all disposed on a semiconductorsubstrate. A first gate electrode is disposed between the photoelectricconversion unit and the charge storage unit on the semiconductorsubstrate, and a second gate electrode is disposed between the chargestorage unit and the floating diffusion unit on the semiconductorsubstrate. This solid-state image pickup apparatus according to oneembodiment also includes a light shielding member including a first partdisposed over the charge storage unit and over at least either the firstgate electrode or the second gate electrode. The light shielding memberalso includes a second part disposed between the first gate electrodeand the second gate electrode and extending from the first part to asurface of the semiconductor substrate. This structure makes it possibleto suppress incidence of oblique light onto the charge storage unit andthus improve the light shielding performance.

Hereinafter, the term “contact plug” is used to describe a plug formedof an electrically conductive material for connecting one member toanother member. Furthermore, in the following description, directionsare defined such that a downward direction is a direction from thesurface of the semiconductor substrate toward the inside of thesemiconductor substrate, and an upward direction is defined as theopposite direction.

First Embodiment

A solid-state image pickup apparatus according to a first embodiment isdescribed below with reference to FIG. 1, FIG. 2A, FIG. 2B, FIG. 3A, andFIG. 3B.

FIG. 1 is a circuit diagram illustrating four pixels (extracted from atotal number of pixels) of the solid-state image pickup apparatusaccording to the present embodiment. In FIG. 1, pixels 100 are arrangedin an array with two rows and two columns. Each pixel 100 includes aphotoelectric conversion unit 101, a charge storage unit 102, a firsttransfer transistor 104, a second transfer transistor 105, an amplifyingtransistor 106, a selection transistor 107, and a reset transistor 108.Each pixel 100 further includes a third transfer transistor 109 servingas an over flow drain (OFD) for discharging an unnecessary charge. Inthe pixel 100, reference numeral 103 denotes a node including a floatingdiffusion (FD) unit. A power supply line 110 and a power supply line 111are wirings for supplying a voltage. The power supply line 110 isconnected to a main electrode region of the OFD transistor 109. Thepower supply line 111 is connected to a main electrode region of thereset transistor 108 and a main electrode region of the selectiontransistor 107. RES, TX1, TX2, SEL, and TX3 denote control lines viawhich pulses are supplied to gate electrodes of the respectivetransistors from a vertical scanning circuit (not shown). Morespecifically, the control line RES is for supplying a pulse to the gateelectrode of the reset transistor 108, the control line TX1 is forsupplying a pulse to the gate electrode of the first transfer transistor104, the control line TX2 is for supplying a pulse to the gate electrodeof the second transfer transistor 105, the control line SEL is forsupplying a pulse to the gate electrode of the selection transistor 107,and the control line TX3 is for supplying a pulse to the gate electrodeof the third transfer transistor 109. OUT denotes a signal line. In FIG.1, n and m are natural numbers indicating particular rows and columns.More specifically, n indicates an n-th row, (n+1) indicates an (n+1)throw adjacent to the n-th row, m indicates an m-th column, and (m+1)indicates an (m+1)th column adjacent to the (m+1)th column. A signaloutput via the signal line OUT is held by a reading circuit (not shown)and subjected to a process such as amplification, addition, etc. Theresultant signal is output to the outside of the solid-state imagepickup apparatus. In this process, a control signal is supplied from ahorizontal scanning circuit (not shown) to control the processing suchas addition on the signal and the outputting of the signal to theoutside. The signal line OUT is connected to an amplifying transistorand a source follower circuit functioning as a constant current source.In FIG. 1, the pixels 100 are basic units forming the photoelectricconversion apparatus, and each pixel includes one photoelectricconversion unit 101.

In the pixels 100 shown in FIG. 1, the global electronic shutteroperation is performed as follows. After an accumulation period has beenelapsed, the charge produced in the photoelectric conversion unit 101 istransferred to the charge storage unit 102 via the first transfertransistor 104. During a period in which the signal charge accumulatedin a certain storage period is stored in the charge storage unit 102,accumulation of a next signal charge in the photoelectric conversionunit 101 is started. The signal charge in the charge storage unit 102 istransferred to the node 103 including the FD part via the secondtransfer transistor 105 and is output as a signal from the amplifyingtransistor 106. To prevent the electric charge, produced in thephotoelectric conversion unit 101 during the period in which the signalcharge is stored in the charge storage unit 102, from intruding into thecharge storage unit 102, the electric charge in the photoelectricconversion unit 101 may be discharged via the third transfer transistor109. The reset transistor 108 sets the node 103 including the FD part toa particular electric potential before the signal charge is transferredfrom the charge storage unit 102 (this operation is called a resetoperation). The electric potential at the node 103 including the FD partat this point of time is output as a noise signal to the signal line OUTvia the amplifying transistor 106. Based on the difference between thissignal and the signal based on the signal charge output later, it ispossible to remove the noise signal.

FIG. 2A is a plan view illustrating a solid-state image pickup apparatuscorresponding to the circuit diagram shown in FIG. 1. FIG. 2B is aschematic cross-sectional view of the solid-state image pickup apparatustaken along line IIB-IIB of FIG. 2A. In FIG. 2A and FIG. 2B, someelements such as a wiring layer, an insulating film, etc., disposed at alevel higher than the level of the gate electrodes are not shown.

In FIG. 2A, pixels 200 correspond to the pixels 100 shown in FIG. 1 andare arranged in an array with two rows and two columns. In this figure,the pixels 200 are virtually partitioned into rectangular regions.Taking one of the four pixels as an example, the structure of the pixelis described below. The pixel 200 includes a photoelectric conversionunit 201 and a charge storage unit 202 disposed close to each other. Agate electrode 204 of a first transfer transistor for transferring anelectric charge is disposed between the photoelectric conversion unit201 and the charge storage unit 202. In the present embodiment, whenseen in plan view, the gate electrode 204 extends such that the chargestorage unit 202 is fully covered with the gate electrode 204. Byproviding the gate electrode 204 such that the charge storage unit 202is fully covered with the gate electrode 204, it becomes possible tosuppress incidence of light on the charge storage unit 202. Furthermore,by controlling a voltage applied to the gate electrode 204 extendingover the charge storage unit 202, it is possible to reduce a darkcurrent in the charge storage unit 202. Note that the main electroderegions of the first transfer transistor include the photoelectricconversion unit 201 and the charge storage unit 202. The pixel 200further includes a gate electrode 205 of a second transfer transistorfor transferring the electric charge from the charge storage unit 202,an FD part 203, a gate electrode 209 of a third transfer transistor. Amain electrode region 207 is disposed adjacent to the gate electrode209. The main electrode region 207 is a region in which an unnecessarypart of the electric charge generated in the photoelectric conversionunit is discharged. The gate electrode 204 functions as the first gateelectrode, and the gate electrode 205 functions as the second gateelectrode.

In FIG. 2A, a contact plug 206 is disposed in the FD part 203 to providea connection between the FD part 203 and a gate electrode of anamplifying transistor and a connection between the FD part 203 and amain electrode region of a reset transistor. A contact plug 208 isdisposed in the main electrode region 207 to provide a connectionbetween the main electrode region 207 and a power supply line. A contactplug 213 is disposed on the second gate electrode 205 to provide aconnection between the second gate electrode 205 and a control line. Thepixel 100 shown in FIG. 1 includes other elements disposed in a region211 shown in FIG. 2A or FIG. 2B. In the present embodiment and otherelements described below, it is assumed that signal charges areelectrons and transistors in the pixel 100 shown in FIG. 1 are N-typeMetal Oxide Semiconductor (MOS) transistors.

The photoelectric conversion unit 201 includes, at least, an N-typesemiconductor region functioning as a charge accumulation unit. Thecharge storage unit includes an N-type semiconductor region capable ofaccumulating an electric charge. The FD part includes an N-typesemiconductor region. The main electrode region 206 of the thirdtransfer transistor includes an N-type semiconductor region. Eachelement is disposed in an active region, and an element isolation region210 is disposed such that the active region is surrounded by the elementisolation region 210. The element isolation region 210 has an isolationstructure such as STI (Shallow Trench Isolation), LOCOS (Local Oxidationof Silicon), or PN junction isolation.

In FIG. 2A, a light shielding member 212 extends over a plurality ofpixels 200. The light shielding member 212 covers the charge storageunit 202 and at least part of the second gate electrode 205. In thepresent embodiment, the light shielding member 212 covers the chargestorage unit 202, the first gate electrode 204, the second gateelectrode 205, and part of the element isolation region 210. As in theexample shown in FIG. 2A, the light shielding member 212 may furtherextend over part, on the side of the first gate electrode 204, of thephotoelectric conversion unit. The light shielding member 212 includes aplurality of openings 214 for the respective contact plugs. The lightshielding member 212 does not exist over a part of the FD part 203 andover a part of the second gate electrode 205. The light shielding member212 may be disposed such that the light shielding member 212 coversother elements in the pixel other than the photoelectric conversion unit201 and regions in which contact plugs are disposed. In the structuredescribed above, the gate electrodes 204 and 205 may be formed using amaterial such as polysilicon, and the light shielding member may beformed using a material such as tungsten, aluminum, etc.

FIG. 2B is a schematic cross-sectional view of the solid-state imagepickup apparatus taken along line IIB-IIB of FIG. 2A. In FIG. 2B, In aP-type semiconductor substrate 220 with a surface 221, an N-typesemiconductor region 222 a of the photoelectric conversion unit 201shown in FIG. 2A and a P-type semiconductor region 223 are formed suchthat the P-type semiconductor region 223 is located closer to thesurface 221 of the semiconductor substrate 220 than the N-typesemiconductor region 222 a is located. In the semiconductor substrate220, an N-type semiconductor region 224 of the charge accumulation unit202 shown in FIG. 2A is also formed. The first gate electrode 204 andthe second gate electrode 205 are disposed on the semiconductorsubstrate 220. The contact plug 206 for connection to the second gateelectrode 205 is disposed on the second gate electrode 205.

In FIG. 2B, the light shielding member 212 shown in FIG. 2A includes afirst part 225 covering the first gate electrode 204 and the second gateelectrode 205 and further includes a second part 226 disposed betweenthe first gate electrode 204 and the second gate electrode 205. Thefirst part 225 and the second part 226 are formed such that a bottomsurface 228 of the second part 226 is located closer to the surface 221of the semiconductor substrate 220 than a bottom surface 227 of thefirst part 225 is located. This structure allows a reduction in theamount of light intruding via the opening 214 for disposing the contactplug 206 and a reduction in intruding of the charge generated by theintruding light into the charge storage unit 202 or the photoelectricconversion unit 201.

The locations of the first part 225 and the second part 226 aredescribed in further detail below. The first part 225 covers the firstgate electrode 204 and the second gate electrode 205 and extends betweenthe first gate electrode 204 and the second gate electrode 205. Thesecond part 226 is disposed such that when seen from above the surface221 of the semiconductor substrate 220 to the surface 221 and when theshapes of the respective parts are projected onto the surface 221, thesecond part 226 is located between the first gate electrode 204 and thesecond gate electrode 205. Furthermore, in cross section takenperpendicular to the surface 221 of the semiconductor substrate 220, thedistance of the bottom surface 228 of the second part 226 from thesurface 221 of the semiconductor substrate 220 is the same as thedistance of the bottom surface 229 of the first gate electrode 204 andthe second gate electrode 205 from the surface 221 of the semiconductorsubstrate 220. The second part 226 may be disposed to satisfy at leastthe condition that the bottom surface 228 of the second part 226 islocated closer to the surface 221 of the semiconductor substrate 220than the bottom surface 227 of the first part 225 is located withrespect to the surface 221 of the semiconductor substrate 220.

In this structure, the first part 225 and the second part 226 areprovided in an integrated form such that the light shielding member 212extends from the first gate electrode 204 to the second gate electrode205 thereby covering the region between the first gate electrode 204 andthe second gate electrode 205, and such that the light shielding member212 extends toward the surface of the semiconductor substrate 220 andbetween the first gate electrode 204 and the second gate electrode 205.Note that in the present embodiment, the upper surface of the first part225 and the upper surface of the second part 226 are substantially flat.If the upper surfaces thereof are not flat, light reflected at the uppersurfaces may become stray light, which may affect the light shieldingperformance in some region. In this regard, the upper surfaces beingflat are advantageous.

When the thickness of light shielding member is denoted by D1 and thedistance between the first gate electrode 204 and the second gateelectrode 205 is denoted by D2, it is desirable to set D1 and D2 suchthat 3×D1≧D2≧1×D1 to achieve good electrical insulation between thefirst gate electrode 204 and the second gate electrode 205 and goodlight shielding performance of the light shielding member 212. If thedistance D2 is too small, there is a possibility that the lightshielding member formed does not extend downward a sufficient distance,which may cause a reduction in the effect of the light shielding memberin terms of the electric field. Conversely, if the distance D2 is toolarge, there is a possibility that there is a region that is not reachedby the electric field extending from the first gate electrode 204 or thesecond gate electrode 205, which may cause an increase in dark currentand/or a reduction in transfer efficiency.

In FIG. 2B, the light shielding member 212 is disposed such that it islocated at the same height as the height of the contact plug 206 (notshown) disposed in the FD part 203 and such that the light shieldingmember 212 is located below a metal wiring layer (not shown). Bydisposing the light shielding member 212 at a location closer to thesurface 221 of the semiconductor substrate 220 than the wiring layer islocated with respect to the surface 221 of the semiconductor substrate220, it is possible to improve the light shielding performance.

The second part 226 shown in FIG. 2B may be formed in a manner describedbelow. After the first gate electrode 204 and the second gate electrode205 are formed, an insulating film such as a silicon dioxide film isformed such that the insulating film covers the first gate electrode 204and the second gate electrode 205 and such that the insulating film hasa shape corresponding to the shapes of the first gate electrode 204 andthe second gate electrode 205. Because the insulating film is formed tohave the shape corresponding to the shapes of the first gate electrode204 and the second gate electrode 205, the surface of the insulatingfilm has a depression. Thereafter, a metal film that is to function asthe light shielding member is formed on the insulating film such thatthe depression of the insulating film is filled with the metal film. Themetal film is then etched such that the metal film is removed except fora particular part that is to function as the light shielding member 212.

Next, referring to FIG. 3A and FIG. 3B, the structure according to thepresent embodiment is further described below. FIG. 3A is a schematiccross-sectional view illustrating the solid-state image pickup apparatusshown in FIG. 2B according to the present embodiment, and FIG. 3B is aschematic cross-sectional view illustrating a solid-state image pickupapparatus with a structure having no second part 226, provided for thepurpose of comparison.

In both FIG. 3A and FIG. 3B, behavior of light is illustrated for a casewhere light is incident at an angle on the opening 214 of the lightshielding member 212. In the structure shown in FIG. 3B, light 302 iseasily incident on elements such as the charge storage unit 202. Evenwhen light 302 is incident on no element, incidence of light 302 on thesemiconductor substrate 220 may generate an electric charge which mayintrude into the charge storage unit 202 or the photoelectric conversionunit 201. The intrusion of the electric charge into the charge storageunit 202 or the photoelectric conversion unit 201 results in noise inthe image signal. On the other hand, in the structure shown in FIG. 3A,the presence of the second part 226 results in a reduction in the amountof light 301 onto the semiconductor substrate 301.

In the present embodiment, the light shielding member 212 covers thecharge storage unit 202, the first gate electrode 204, and the secondgate electrode 205. More specifically, the light shielding member 212extends over the whole areas of the above-described elements except forcontact plugs thereof. Note that the light shielding member 212 may beformed such that at least a part, on the side of the charge storage unit202, of the first gate electrode 204 or the second gate electrode 205 iscovered by the light shielding member 212. If the light shielding member212 is disposed such that it extends only over the charge storage unit202, the charge storage unit 202 are not completely covered by the lightshielding member 212 and more particularly an edge thereof facing thefirst gate electrode or an edge thereof facing the second gate electrode205 is no covered by the light shielding member 212. By providing thelight shielding member 212 such that the gate electrodes are covered atleast partially by the light shielding member 212, it is possible tocompletely cover the charge storage unit 202 by the light shieldingmember 212. However, even in this structure, there is a possibility thatintrusion of light may occur as in the structure shown in FIG. 3B. Sucha possibility may be reduced by providing the second part 226 as shownin FIG. 3A.

In the solid-state image pickup apparatus according to the presentembodiment, as described above, oblique incidence of light on the chargestorage unit is suppressed and thus an improvement in the lightshielding performance is achieved. Although in the present embodiment,there is no contact plug for connecting the first gate electrode to thecontrol line, an opening similar to the opening 214 may be formed in thelight shielding member 212 and a contact plug for this purpose may bedisposed in the opening. Alternatively, the first gate electrode mayextend into a region in an adjacent pixel and a contact plug may bedisposed in this region.

Second Embodiment

A solid-state image pickup apparatus according to a second embodiment isdescribed below with reference to FIG. 4A and FIG. 4B. FIG. 4A is aschematic plan view of the solid-state image pickup apparatus, and FIG.4B is a schematic cross-sectional view of the solid-state image pickupapparatus taken along line IVB-IVB of FIG. 4A. FIG. 4A and FIG. 4Bcorrespond to FIGS. 2A and 2B, respectively, and similar elements tothose in FIG. 2A or FIG. 2B are denoted by similar reference symbols,and a further description thereof is omitted.

The structure shown in FIG. 4A is different from that according to thefirst embodiment in that it has a contact plug 401. The contact plug 401is provided for electrically connecting the light shielding member 212to the first gate electrode 204. In this structure, it is not necessaryto produce an opening for the contact plug in the light shielding member212, and thus it is possible to achieve high light shieldingperformance. Furthermore, in this structure, the light shielding member212 may also function as a control line for supplying a voltage to thefirst gate electrode 204, which allows a reduction in the number ofwirings.

As shown in FIG. 4B, the contact plug 401 is disposed between the firstgate electrode 204 and the first part 225 of the light shielding member212. An insulating film made of, for example, silicon dioxide isdisposed between the first gate electrode 204 and the first part 225. Acontact hole is formed in this insulating film and the contact hole isfilled with an electrically conductive material thereby forming thecontact plug 401. Alternatively, after the contact hole is formed in theinsulating film, a metal film that is to function as the light shieldingmember 212 may be formed thereby simultaneously forming the contact plug401 and the light shielding member 212. The process of forming theseelements is accomplished using common semiconductor fabricationtechnology, and thus a further detailed description thereof is omitted.

As shown in FIG. 4B, the light shielding member 212 also includes thesecond part 226 which brings about an improvement in light shieldingperformance. Note that an N-type semiconductor region 402 shown in FIG.4B forms an FD region 203 shown in FIG. 4A.

In the solid-state image pickup apparatus according to the presentembodiment, as described above, oblique incidence of light on the chargestorage unit is suppressed and thus an improvement in the lightshielding performance is achieved. Furthermore, the connection betweenthe light shielding member and the first gate electrode allows areduction in the number of openings, for the contact plugs on the firstgate electrode, in the light shielding member, which brings about animprovement in light shielding performance.

Third Embodiment

A solid-state image pickup apparatus according to a third embodiment isdescribed below with reference to FIG. 5A and FIG. 5B. FIG. 5A is aschematic plan view of the solid-state image pickup apparatus, and FIG.5B is a schematic cross-sectional view of the solid-state image pickupapparatus taken along line VB-VB of FIG. 5A. FIG. 5A and FIG. 5Brespectively correspond to FIGS. 2A and 2B, and also to FIG. 4A and FIG.4B, and similar elements to those in FIG. 2A or FIG. 2B or FIG. 4A orFIG. 4B are denoted by similar reference symbols, and a furtherdescription thereof is omitted.

The structure shown in FIG. 5A is different from that according to thesecond embodiment in that it has not the contact plug 401 shown in FIG.4A but a contact plug 501. The contact plug 501 is provided forelectrically connecting the light shielding member 212 to the secondgate electrode 205. In this structure, it is not necessary to produce anopening for the contact plug in the light shielding member 212, and thusit is possible to achieve high light shielding performance. Furthermore,in this structure, the light shielding member 212 may also function as acontrol line for supplying a voltage to the second gate electrode 205,which allows a reduction in the number of wirings.

As shown in FIG. 5B, the contact plug 501 is, as with the contact plug401 according to the second embodiment, is formed in an insulating filmdisposed between the second gate electrode 205 and the first part 225 ofthe light shielding member 212. This structure is similar to thatassociated with the contact plug 401 according to the second embodiment,and thus a further detailed description thereof is omitted.

As shown in FIG. 5B, the light shielding member 212 also includes thesecond part 226 which brings about an improvement in light shieldingperformance. In the solid-state image pickup apparatus according to thepresent embodiment, as described above, oblique incidence of light onthe charge storage unit is suppressed and thus an improvement in thelight shielding performance is achieved. Furthermore, the connectionbetween the light shielding member and the second gate electrode allowsa reduction in the number of openings for contact plugs in the lightshielding member, which brings about an improvement in light shieldingperformance.

Fourth Embodiment

A solid-state image pickup apparatus according to a fourth embodiment isdescribed below with reference to FIGS. 6A to 6C. FIG. 6A is a schematicplan view of the solid-state image pickup apparatus, FIG. 6B is aschematic cross-sectional view of the solid-state image pickup apparatustaken along line VIB-VIB of FIG. 6A, and FIG. 6C is a schematiccross-sectional view of the solid-state image pickup apparatus takenalong line VIC-VIC of FIG. 6A. FIG. 6A corresponds to FIG. 2A. FIG. 6Band FIG. 6C correspond to FIG. 2B. In FIGS. 6A to 6C, similar elementsto those in FIG. 2A or FIG. 2B are denoted by similar reference symbols,and a further description thereof is omitted.

As shown in FIG. 6A and FIG. 6C, the present embodiment is differentfrom the first embodiment in that the first gate electrode 204 does notcover completely over the whole area of the charge storage unit 202.That is, the first gate electrode 204 extends over part of the N-typesemiconductor region 222 and part of the N-type semiconductor region224. In this structure, the light shielding member 212 is disposed overthe charge storage unit 202 and over at least part of the second gateelectrode 205. The light shielding member 212 further extends over thefirst gate electrode 204 and over part of the element isolation region210. The light shielding member 212 covers the first gate electrode 204and part, on the side of the first gate electrode 204, of thephotoelectric conversion unit 201.

Also in this structure, as shown in FIG. 6B, the light shielding member212 further includes a second part 226 disposed between the first gateelectrode 204 and the second gate electrode 205. The presence of thesecond part 226 results in a suppression of oblique incidence of lighton the charge storage unit, and thus an improvement in the lightshielding performance is achieved. In FIG. 6A, reference numeral 601denotes a contact plug that is disposed on the first gate electrode 204such that it is in contact with the first gate electrode 204 and that isfor supplying a voltage to the first gate electrode 204.

The solid-state image pickup apparatus according to any one of theembodiments described above may be applied to, for example, an imagepickup system including the solid-state image pickup apparatus asdescribed below. Note that the term “image pickup system” is used todescribe a wide variety of systems including an apparatus whose mainpurpose is to take an image such as a still camera, a video camera,etc., and an apparatus having an image-taking function as an auxiliaryfunction such as a personal computer, a portable terminal, etc. Theimage pickup system includes a solid-state image pickup apparatusaccording to one of the embodiments described above and a processingunit that processes a signal output from the solid-state image pickupapparatus. The processing unit may include, for example, a digital dataprocessor.

In the solid-state image pickup apparatus according to the presentembodiment, as described above, oblique incidence of light is suppressedand thus an improvement in the light shielding performance is achieved.Thus, a reduction in intrusion of noise into an image signal isachieved, and thus a high-quality image may be obtained.

The solid-state image pickup apparatus is not limited to the embodimentsdescribed above, but various modifications are possible. For example,conduction types of the transistors and the semiconductor regions may beinverted, and/or transistors of different conduction types may becombined. Note that techniques disclosed in the embodiments describedabove may be combined.

While the disclosure has been described with reference to exemplaryembodiments, it is to be understood that embodiments are not limited tothe disclosed exemplary embodiments. The scope of the following claimsis to be accorded the broadest interpretation so as to encompass allsuch modifications and equivalent structures and functions.

This application claims the benefit of Japanese Patent Application No.2011-119258 filed May 27, 2011, which is hereby incorporated byreference herein in its entirety.

1. A solid-state image pickup apparatus comprising: a semiconductorsubstrate; a photoelectric conversion unit disposed on the semiconductorsubstrate; a charge storage unit that is disposed on the semiconductorsubstrate and that stores an electric charge generated in thephotoelectric conversion unit; a floating diffusion unit which isdisposed on the semiconductor substrate and to which the electric chargestored in the charge storage unit is transferred; a first gate electrodedisposed on the semiconductor substrate such that the first gateelectrode extends between the photoelectric conversion unit and thecharge storage unit and such that the first gate electrode reaches thecharge storage unit; a second gate electrode disposed on thesemiconductor substrate such that the second gate electrode extendsbetween the charge storage unit and the floating diffusion unit; and alight shielding member including a first part and a second part whereinthe first part is disposed over the charge storage unit and at leastover the first gate electrode and the second gate electrode, and whereinthe second part is disposed between the first gate electrode and thesecond gate electrode such that the second part extends from the firstpart toward a surface of the semiconductor substrate.
 2. The solid-stateimage pickup apparatus according to claim 1, further comprising a plugdisposed on the second gate electrode and configured to supply a voltageto the second gate electrode, wherein the light shielding memberincludes an opening surrounding the plug.
 3. The solid-state imagepickup apparatus according to claim 1, wherein when the thickness of thelight shielding member is denoted by D1 and the distance between thefirst gate electrode and the second gate electrode is denoted by D2, D2and D1 satisfy a condition described below:3×D1≧D2≧1×D1.
 4. The solid-state image pickup apparatus according toclaim 1, wherein the light shielding member extends over part, on a sideof the first gate electrode, of the photoelectric conversion unit. 5.The solid-state image pickup apparatus according to claim 1, furthercomprising a plug functioning as a contact connecting the first gateelectrode to the light shielding member.
 6. The solid-state image pickupapparatus according to claim 1, further comprising a plug functioning asa contact connecting the second gate electrode to the light shieldingmember.
 7. The solid-state image pickup apparatus according to claim 1,further comprising a plurality of wiring layers, wherein the lightshielding member is located closer to the semiconductor substrate thanthe wiring layers are located with respect to the semiconductorsubstrate.
 8. The solid-state image pickup apparatus according to claim1, wherein an upper surface of the first part and an upper surface ofthe second part are substantially flat.
 9. An image pickup systemcomprising: the solid-state image pickup apparatus according to claim 1,and a processing unit that processes a signal output from thesolid-state image pickup apparatus.